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Date: Fri, 28 Jun 2013 11:56:29 +0100
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
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Subject: Re: [Qemu-devel] [PATCH v2] xen_disk: support "direct-io-safe"
 backend option
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To: Alex Bligh <alex@alex.org.uk>
Cc: xen-devel@lists.xensource.com, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Ian Jackson <Ian.Jackson@eu.citrix.com>, qemu-devel@nongnu.org, Anthony Liguori <anthony@codemonkey.ws>, Paolo Bonzini <pbonzini@redhat.com>

On Fri, 28 Jun 2013, Alex Bligh wrote:
> Stefano,
> 
> --On 27 June 2013 19:16:30 +0100 Stefano Stabellini
> <stefano.stabellini@eu.citrix.com> wrote:
> 
> >  *      Therefore this option gives the backend permission to use
> >  *      O_DIRECT, notwithstanding that bug.
> 
> Looks useful. Are you planning to do this for both emulated and pv
> disks?

This is PV only, at least for the moment: emulated disks always use
writeback caching.
>>From the performance point of view, making this change for IDE disks is
not very important (because IDE is slow anyway).

From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Subject: Re: [PATCH v2] xen_disk: support "direct-io-safe"
 backend option
Date: Fri, 28 Jun 2013 11:56:29 +0100
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To: Alex Bligh <alex@alex.org.uk>
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List-Id: xen-devel@lists.xenproject.org

On Fri, 28 Jun 2013, Alex Bligh wrote:
> Stefano,
> 
> --On 27 June 2013 19:16:30 +0100 Stefano Stabellini
> <stefano.stabellini@eu.citrix.com> wrote:
> 
> >  *      Therefore this option gives the backend permission to use
> >  *      O_DIRECT, notwithstanding that bug.
> 
> Looks useful. Are you planning to do this for both emulated and pv
> disks?

This is PV only, at least for the moment: emulated disks always use
writeback caching.
>>From the performance point of view, making this change for IDE disks is
not very important (because IDE is slow anyway).